# How Do Supernovae Impact the Circumgalactic Medium? I. Large-Scale Fountains Around a Milky Way-Like Galaxy

**Authors:** Miao Li, Stephanie Tonnesen  
**arXiv:** [1910.14235](https://arxiv.org/abs/1910.14235)  
**Date:** 2019-10-31  
**Summary page:** https://www.summarizepaper.com/en/paper/1910.14235v2/

## Key points

- Authors investigate the role of feedback in galaxy formation and its impact on large scales
- Limitations of cosmological simulations due to ad hoc feedback parameters and lacking resolutions
- Small-box simulations provide better resolution but fail to capture gas evolution beyond their domain
- Authors implement small-box results of supernovae-driven outflows into dark matter halo-scale simulations
- Focus on studying effects of galactic outflows, particularly hot phase carrying most energy and metals
- Hot outflows incorporated into idealized simulations of a Milky Way halo to analyze impact on circumgalactic medium (CGM)
- Low star formation surface density leads to gravitationally bound hot outflows within the halo
- Outflows form metal-enriched atmosphere with fountain motions at large scale, creating equilibrium between condensation of cool gas and injection of hot outflows
- Self-regulated atmosphere exhibits radially decreasing temperature distribution, producing observed X-ray luminosity and column densities of O VI, O VII, and O VIII
- Estimated baryon and metal masses in the atmosphere are relatively small compared to "missing" baryons and metals from halos
- Propose that missing materials may reside at larger radii potentially ejected by more powerful outflows in past times

## Summary

In the study titled "How Do Supernovae Impact the Circumgalactic Medium? I. Large-Scale Fountains Around a Milky Way-Like Galaxy," authors Miao Li and Stephanie Tonnesen investigate the role of feedback in galaxy formation and its impact on large scales. They address the limitations of cosmological simulations which often rely on ad hoc feedback parameters due to lacking resolutions. On the other hand, small-box simulations provide better resolution but fail to capture gas evolution beyond their simulation domain. To bridge this gap, the authors implement small-box results of supernovae-driven outflows into dark matter halo-scale simulations and focus on studying their effects on large scales. They specifically examine galactic outflows which are multiphase in nature; however, small-box simulations reveal that the hot phase (with temperatures around 10^6-10^7 K) carries most of the energy and metals. The researchers incorporate hot outflows into idealized simulations of a Milky Way halo and analyze their impact on the circumgalactic medium (CGM). They particularly focus on scenarios where star formation surface density is low, resulting in gravitationally bound hot outflows within the halo. The findings indicate that these outflows form a metal-enriched atmosphere with fountain motions at a large scale. This leads to condensation of cool gas at a rate that balances with the injection of hot outflows; thus creating an equilibrium between these processes which gives rise to a universal density profile for the hot atmosphere independent of mass outflow rate. Furthermore, this self-regulated atmosphere exhibits a radially decreasing temperature distribution naturally producing observed X-ray luminosity as well as column densities of O VI, O VII, and O VIII. The authors estimate that this atmosphere contains baryon and metal masses of approximately (0.5 - 1.2) x 10^10 solar masses and (0.6 - 1.4) x 10^8 solar masses respectively; values which are relatively small compared to what is known as "missing" baryons and metals from halos. Based on these results they propose that such missing materials may reside at even larger radii potentially ejected by more powerful outflows in past times; highlighting further investigation into mechanisms and dynamics behind galactic outflows for better understanding their role in galaxy formation and evolution overall.